Piezoelectric device



Filed. Oct. 20, 1944 Zwmw @www Patented Mar. 4, 1947 PIEZOELECTRC DEVICE Raymond W. Tibbetts, Camden, Maine, assigne-1;

to Tibbetts Laboratories, Inc., Camden, Maine:l a. corporation of Maine Application october zo, 1942i, serial No. 559,522'

in claims. (ci. 1v1- 327i This invention relates to piezo-electric devices for converting electrical energy into mechanical `vibrations or converting mechanical energy into slab from an external circuit or from the piezoelectric slab to an external circuit. The invention is applicable to the ordinary piezo-electric device of the type comprising two layers cemented together with their axes extending in diiierent directions, so that when one layer contracts in one direction the other layer expands in the same direction at the Sametime .to cause the slab to warp. The invention is also applicable to piezo-electric devices of the type disclosed in my prior Patent 2,386,279, granted October 9, 1945, which requires only one layer and, if there be more than one layer, the axes of all the layers extend in the same direction. Instead of warp.. ing, the device expands and contracts diagonally, alternately expanding and contracting along each diagonal.

The device of the present invention comprises a piezolectric slab which maybe formed in one layer or a plurality of layers, together with means for passing current between the slab and an ex ternal circuit, the means including a layer of conducting material extending overone face of the slab. Preferably the conducting material is metal foil, with or without a superposed coatlng of colloidal or partially colloidal graphite or other suspension ot conducting material, such as According to the present invention each lead l is anchored to the slabby means of a body of cement disposed in a recess in the slab so that when the cement shrinks in setting it draws the lead toward the slab. The body'of cement may be placed in the recess either before or after the lead is placed in position. However if the recess extends all the Way through the slab it is f preferable to place the lead over the hole and then illl the opening from the opposite side of the slab. I! the opening also extends through the lead the opposite ends oi the plug may overlap the lead on one side and the slab ori-the other side like a rivet. However it is unnecessary to have any opening in the lead. While the cement may extend out between the lead and slab around the opening this is also unnecessary. in drying or otherwise settingthe shrinkage of the cement plug draws the lead snugly against the side oi the slab. When the cement plug extends all the way through the slab it should of course be non-conducting; otherwise it would short circuit the two electrodes. While any suitable cement may be employed cellulose nitrate in a suitable solvent is recommended.

For the purpose of illustration a typical embodiment of the invention is shown in the ac-l companying drawings in which Fig. l is a perspective view of the device;

Fig. 2 is a similar view of the slab and leads;

Fig. 3 is a section of line 3-3 of Fig. 1; and

Fig. e is a section o! line t-d of Fig. 2.

The particular embodiment of the invention chosen for theY purpose oi illustration resembles that disclosed in the aforesaid application in that it comprises a piezo-electric-slab i, the slab being cut from the original crystal so that it expands alternately, in response to alternating current, along its two diagonals. Extending along one diagonal on one side of the frame is a toggle I and extending along the other diagonal along the other side ci. the device is a toggle Il, each toggle being in the form o1 a bow arched away from the slab in the middle and having its ends cemented or otherwise secured to the corners oi slab. .'iie two toggles a and d are inter connected by a rod d which rmay be connected to e. microphone, speaker or the like depending upon the'use to which the device is to be put.

The faces ci the slab l are covered with layers 'i .and il ci conducting material which is pref= t erably gold leaf. Conductorslii and l2 are corinecteci to the conducting layers 'l and 8 for transmitting current to or from the device. The device may be mounted on rubber feet lo.

as :fully described in the aforesaid application the slab expands along one diagonal when cur rent hows through the slab in one direction and it expands along the other diagonal when current flows in the opposite direction. When the slab expands along one diagonal it contracts along the other diagonal. Consequently when the slab expands in the direction of the bow 3 the bow straightens and the bow 4 arches farther away from the slab. Thus both bows tend to move the rod d downwardly (Figs. 2 and 3). Conversey when the slab expands in the direc= tion of the bow l both bows tend to move the rod 6 upwardly.

In accordance with the present invention leads Il and l2 are anchored to the slab by cement plugs i3 which extend through openings in the slab and leads. While the opening may be filled before the lead is placed on the slab, preferably the lead is placed over the hole and cement is then applied from the opposite side. Upon setting the shrinkage of the cement draws the lead tightly against the slab. The aforesaid coatings of graphite or the like are .then applied over the faces of the slab and over the leads II and I2, as indicated at I8 and I9. While these graphite coatings may extend over the entire faces of the slab, it is usually suiiicient to have them extend only throughout small parts of the faces of the slab as indicated in the drawings.

From the foregoing it will be understood that current ilows through the lead II and coating I8, thence through the gold leaf electrode l', thence through the slab and thence through the electrode 8, coating I9 and conductor I2. By virtue of the plugs I3 which anchor the leads to the slab, the leads do not tend to pull loose or break oi in use.

As disclosed in the aforesaid application the entire device may be covered with a moistureproof coating ,such as cellulose nitrate, polystyrene, a Vinylite plastic dissolved in a suitable solvent, et cetera, the solution being sprayed on or otherwise applied in layers, each layer being dried before the next layer is applied.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. In a device of the character described the combination of a piezo-electric slab, and means for passing current between the slab and an external circuit, said means including a lead overlapping one side of the slab, the lead comprising a sheet of conducting material laid along one side of the slab parallel with the adjacent face of the slab, and a body of cement anchoring the lead on the slab, said body being disposed in a recess in the slab so that when the cement shrinks in setting it draws the lead toward the slab.

2. In a device of the character described the combination of a piezo-electric slab, thin conducting layers mounted on opposite faces of the slab for conducting current to and from the slab, and leads for connecting said layers to an external circuit, each lead comprising a sheet of conducting material laid over one of said layers parallel with the adjacent face of the slab, and a body of cement anchoring each lead on the slab, each body being disposed in a recess in the slab so that when the cement shrinks in setting it draws the lead toward the slab.

3. In a device of the character described the combination of a piezo-electric slab, and means for passing current between the slab and an external circuit, said means including a sheet of metal foil extending over said slab parallelv to its adjacent face, and a body of cement anchoring the foil n the slab, said body being disposed in a recess in the slab so that when the cement shrinks in setting it draws the foil toward the slab.

4. In a device of the character described the combination of a piezo-electric slab, and means for passing current between the slab and an external circuit, said means including a lead overlapping one side of the slab, the lead comn prising a sheet of conducting material laid parallel with the adjacent face of the slab, and a body of cement anchoring the lead on the slab, said body being disposed in an opening extending through the slab so that the cement may be poured into the opening from the side of the slab opposite to the lead.

5. In a device of the character described the combination of a piezo-electric slab, thin conducting layers mounted on opposite faces of the slab for conducting current to and from the slab, and leads for connecting said layers to an external circuit, each lead comprising a sheet of conducting material laid over one oi Said layers parallel with the adjacent face of the slab, and a body of cement anchoring each lead on the slab, each body being disposed in an opening extending through the slab so that the cement may be poured into the opening from the side of the slab opposite to the lead, the cement being nonn conducting so that it does not short-circuit said conducting layers.

6. In a device of the character described the combination of a piezo-elcctric slab, and means for passing current between the slab and an external circuit, said means including a sheet oi metal foilv extending over said slabl parallel to its adjacent face, and a body of cement anchoring the foil on the slab, said body being disposed in an opening extending through the slab so that the cement may be poured into the opening from the side of the slab opposite to the lead.

"7. In a device 'of the character described the combination of a piezo-electric slab, and means for passing current between the slab and an external circuit, said means including a lead overlapping one side of the slab, the lead comprising a sheet of conducting material laid parn allel with the adjacent face of the slab, a body of cement anchoring the lead on the slab, said body being disposed in a recess in the slab so that when the cement shrinks in setting it draws the lead toward the slab, and a coating of conn ducting material adhering to the slab and lead and extending across the edge of the lead.

8. In a device of the character described the combination of a piezo-electric slab, and means for passing current between the slab and an external circuit, said means including a sheet of metal foil extending over said slab parallel to its adjacent face, a body of cement anchoring the foil on the slab, said body being disposed in an opening extending through the slab so that the cement may be poured into the opening from the side of the slab opposite to the sheet, and a coating of graphite adhering to the slab and lead and extending across the edge oi the lead.

9. In a device of the character described the combination of a piezo-electric slab, and means for passing current between the slab and an` external circuit, said means including a lead overlapping one side of the slab, the lead comprising a sheet of conducting material laid along one side of the slab parallel with the adiacent face 0i the.

slab, and a body oi cement anchoring the lead on the slab, said lead having an opening therethrough and said body extending through the opening.

10. In a device of the character described the combination of a piezo-electric slab, thin conducting layers mounted on opposite faces or" the slab for conducting current to and from the slab,

and leads for connecting said layers to an external circuit, each lead comprising a sheet of con- REFERENCES CITED ducting material laid over one of said layers parand with the adjacent :ace of the slab, and a mrfr; ftrllilsvggtferens are of record i the body of cement anchoring each lead on the slab, v

said layer and lead on each side of the slab hav- 5 UNITED STATES PATENTS ing registering openings and said body extending Number Name Date through mth Openins- 1 e36 83o Nicol on .m1 26 1927 RAYMOND w. mBETrs. s y 

